Various imaging methods are known in modern medicine for obtaining a comprehensive knowledge of specific organs and their conditions essentially without opening the body. X-ray systems, computed tomography systems, magnetic resonance systems and ultrasound systems are examples of appropriate imaging systems. Such systems and/or units are usually denoted as modalities.
A multiplicity of control parameters must be adjusted in order to use an imaging modality in order to obtain sufficiently good images of a structure and/or an organ, for example a bone structure, the brain, the heart, the lung, the gastrointestinal area etc for a specific set of questions forming the basis of the examination. Thus, for example, it is necessary to adjust the most varied technical control parameters such as voltage, current, slice thickness, pitch, rotational speed etc in the case of computed tomography systems. In the case of systems of recent generations, it is becoming ever more complex to adjust all the control parameters optimally.
In order to carry out an examination in a way that is as friendly as possible to the patient, the control parameters should be adjusted during the examination such that the images produced exhibit an image quality sufficient for the respective examination in conjunction with as low a radiation dose as possible. In this case, there should be a high measure of operator friendliness. In order to avoid errors as far possible during adjustment, the operation should advantageously proceed as intuitively as possible.
Modern imaging systems already offer for the most varied body regions selected measurement protocols that prescribe specific control parameter sets for the various types of examination and/or for the clinical problems on which the examination is based. Thus, for example, in the meantime substantially more than 100 different protocols are available on computed tomography systems in the high-end region, for example. The various measurement protocols then further require to be adapted manually to the precise examination problem and to the patient-specific geometry.
In particular, in the case of a computed tomography system, for example, the tube current, and thus the dose—must be adapted to the so-called patient profile, that is to say to the size and the weight of the patient. This is because the attenuation, and thus the image quality, depends on the thickness of the patient's body in the beam direction. Thus, given a relatively strong patient profile there is a need for a relatively high tube current in order to achieve the same image quality as in the case of a relatively thin patient profile. Even in the most modern systems, it has only been possible to date to automatically fit the tube current, but not the tube voltage, for example, to the patient profile.
As a rule, an operator of such a system selects and adapts the suitable protocols on the basis of his experience with such examinations. It can therefore by all means occur with inexperienced examiners that insufficient examination results are obtained owing to unfavorable parameter constellations. In the extreme case, this can necessitate a repetition of the examination given an excessively low image quality. The additional radiation burden caused thereby in a computed tomography system, for example, is not inconsiderable for the patient.
The same holds in the case of magnetic resonance examinations, where the patient is exposed to an additional unnecessary high-frequency burden. On the other hand, even an excessively high image quality that is not required per se for the examination that is to be carried out, because it is associated with no additional gain of information, or only a very slight one, leads only to an additional burden for the patient. Added to this in the case of computed tomography examinations and, in particular, magnetic resonance examinations is the fact that measurements that may have been carried out with an unnecessarily high image quality lead to an unnecessarily long measuring time, and this renders the measurement as a whole more expensive.